* Dual motors and skid steering. Motors, gearboxes and wheels are already assembled and mounted on a chassis. Not the best of chassis but still it's workable. The motors where designed to run at 6V at full speed, but we don't need nearly the top speed this toy was meant to do so four rechargeable AA batteries (4.8V) should work fine.
* The printed circuit board that drives the toy itself is a basic single sided board with though-hole components, not surface mount. This is the key thing that makes this toy a sweet hackable deal. It has a transistor based H-bridge with forward and reverse for each motor. You can hack into the PCB with a little desoldering and presto, that dual channel h-bridge is now doing your bidding.
* The data signals for the h-bridge can be plain old 5v, straight out of your microcontroller. It will probably work with 3.3V signals as well, I just haven't tried it.
* As mentioned the chassis is OK but not great. Still, it allows me to mount my normal setup for this sort of thing, a solderless breadboard with an arduino clone attached. (The DC boarduino from adafruit industries).
* The built-in battery case takes (4) AA's. Four rechargeable ones works out great as the motor power supply.
* They even give you a 9V battery which I use to power the microcontroller via the boarduino's voltage regulator. Having separate batteries for the motors (the rechargable AA's) and for the data/control electronics (microcontrollers, sensors, etc) is a good idea to cut down on interference problems.